$A$ lead bullet moving with velocity $V$ strikes a wall and stops. If $75 \%$ of its energy is converted into heat,then the increase in temperature is ($s=$ specific heat of lead,$J=$ mechanical equivalent of heat).

Two objects made of the same material have masses $m$ and $2m$ and are at temperatures $2T$ and $T$ respectively. When heat $Q$ is supplied to the object of mass $2m$, its temperature rises to $2T$. If the same heat $Q$ is supplied to the object of mass $m$, its temperature rises to:

Calculate the amount of heat (in calories) required to convert $5\,g$ of ice at $0^{\circ}C$ to steam at $100^{\circ}C$.

Which form of heat was believed in before the modern time?

An electric heater with a constant heat supply rate is used to convert a certain amount of liquid ammonia to saturated vapour at high pressure. The heater takes $14 \text{ minutes}$ to bring the liquid at $15^{\circ}C$ to the boiling point of $50^{\circ}C$ and $92 \text{ minutes}$ to convert the liquid at the boiling point wholly to vapour. If the specific heat capacity of liquid ammonia is $4.9 \text{ kJ/kg K}$, the latent heat of vaporisation of ammonia in $\text{kJ/kg}$ is:

$A$ calorimeter of mass $0.2 \ kg$ and specific heat $900 \ J/kg \cdot K$ contains $0.5 \ kg$ of a liquid of specific heat $2400 \ J/kg \cdot K$. Its temperature falls from $60^{\circ}C$ to $55^{\circ}C$ in one minute. The rate of cooling is ....... $J/s$.